To monitor the prevalence of HIV risk behaviors, HIV infection, and the use of HIV prevention programs among populations at increased risk for HIV, the Los Angeles County Department of Public Health's (LACDPH) HIV Epidemiology Program proposes to implement an HIV behavioral surveillance system during 2011-2015. The system will involve alternating cross-sectional surveys among men who have sex with men (MSM), injecting drug users (IDU), and heterosexuals at risk for HIV infection (HET) using both venue-based and respondent- driven sampling methods. The collected behavioral data will be used to inform local HIV prevention planning as well as to contribute to a national HIV behavioral surveillance (NHBS) database. The overall goal of this proposal is to maintain our NHBS system for monitoring long-term trends in HIV risk behaviors among high-risk populations in Los Angeles County. In addition, we are proposing three supplemental research activities that will allow us to a) help develop new HIV-testing technologies during our third MSM cycle;b) estimate the prevalence of hepatitis B and C in MSM, IDU, and HET populations;and c) conduct one cycle of NHBS with a minimum of 200 male-to-female transgender persons (TG) of all races/ethnicities. To accomplish these goals, we have identified the following specific aims: 1. Conduct annual behavioral surveys. We will monitor the prevalence of HIV risk behaviors and access to and use of HIV prevention programs by administering standardized questionnaires among MSM, IDU, heterosexual, and male-to-female transgender persons at risk of HIV infection across six NHBS cycles in Los Angeles County. 2. Offer HIV and hepatitis B and C testing. We will provide rapid and standard HIV testing services to NHBS participants and use these outcome data to estimate HIV prevalence and incidence. We will also offer screening tests to detect evidence of hepatitis B and C infection across five NHBS cycles and offer participation in developing new HIV testing technologies during NHBS-MSM3. 3. Collaborate with local partners. We will engage local researchers in qualitative research activities and we will work with local community agencies to co-develop local-use survey questions and implementation strategies. 4. Evaluate the NHBS system. We will work collaboratively with CDC to monitor the local quality, efficiency, and value of NHBS data collection and implementation methods.